Sand bed

[Moogled]

Look at all these converters.

To think of all the fights that were put up in terms of pro-DSB.

[andsoitgoes]

Ugh - This is an interesting debate, and one that I'm VERY frustrated about primarily because my tank is already set up :P

And also cuz I have some wicked nassarus (sp?) snails in there.

What are everyones thoughts on slowly taking bits out each water change until the sand is maybe 1/2" deep?

I don't want go to BB....

[DJKoop]

For those not familiar with a plenum here is an example.

To assemble the plenum follow these directions
1. The egg crate usually comes in 2' x 4' sheets and can be found in most hardware stores like Lowes and Home Depot. Cut the egg crate to size (A pair of heavy utility scissors works well.)
2. Place the Egg Crate panel on a flat surface..
3. Attach the PVC pipe rails to the egg crate using nylon tie wraps (no metal).
4. Attach the PVC pipe ends to the egg crate.
5. Space the PVC pipe supports evenly on the egg crate and attach.
6. Turn the assembly over.
7. Cut a hole in the Egg Crate large enough for the 1" riser tube to fit into. This hole can be anywhere you want it.
8. Cover the assembly with the larger piece of nylon screening and tie-wrap in place. It should hang over the sides.
9. Cut a V-shaped grove in one end of the riser tube with a small saw. This will allow the riser to sit on the bottom of the tank while water moves freely.
10. Cut the screening where the riser tube goes and insert the riser tube with the grove in first.
11. Place the plenum assembly in the tank and center it.
Cover the plenum with approximately 1 to 2 inchs of CaribSea "Seaflor special Grade Reef Sand.
12. Lay the smaller piece of screening in the tank centered. This helps keep burrowing critters from disturbing the bottom layer of sand.
Cover the screen with the rest of the CaribSea "Seaflor special Grade Reef Sand.
13. Install a Power head on the riser tube and run it until Amonia and Nitrite readings are undetectable, then remove the power head and riser tube.

Images:

http://i163.photobucket.com/albums/t.../PlenumTop.gif
http://i163.photobucket.com/albums/t...PlenumSide.gif

[BCOrchidGuy]

I like sand but there is no doubt it's an area that causes a lot of debate. Right now I'm setting up a tank and I'm pretty sure I'll go BB, I was thinking of some sand in a refugium that sits beside my sump but other than that I think I'll avoid it. If you do go with sand I'd say look at building a coil denitrator and getting it going while your getting your tank settled in.

Doug

[DJKoop]

The main idea behind a plenum is that you run it with a power head in a new system to get your levels straight. After that you remove the riser tube and power head and the empty space under the sand bed is where your denitrafying bacteria live and do their job.

[albert_dao]

You're still not addressing the accumulation of detritus. Nitrate is one of the lesser evils caused by detritus buildup. Other organics/toxins (phosphates, gases) can build up in the presence of large detritus deposits, plenum or DSB notwithstanding.

[Doug]

I would not use the powerhead method myself. Nothing wrong with the riser for allowing the removal of plenum water, {very slowly}, at times. But thats an alternative way and not from the original way Dr. Jaubert published.

Plus I did the course/fine sandbed. If I did one again I would use 4in. of a course media between 3mm to 5mm. This would allow for better water movement through the gravel & plenum. Needs to be deep enough though, with the larger sized grains, so to much oxygen does not penetrate.

Plus I would limit the amount of rock to minimum and elevate what there was. This, of course, is my opinion on running one, as opposed to the plenum systems ran in the 90,s. I have not tested this yet, but others agree with this senario.

The biggest problem is the loss of 6in. of tank space. Of course the sandbed authors figure a plenum is a waste. compared with their dsb ideas. And the bare bottomed aquarists figure both are a waste. I have seen great tanks with all three. Guess it depends on what one wishes to apply to their situation, and the livestock one wishes to keep.

[Doug]

Originally Posted by albert_dao

You're still not addressing the accumulation of detritus. Nitrate is one of the lesser evils caused by detritus buildup. Other organics/toxins (phosphates, gases) can build up in the presence of large detritus deposits, plenum or DSB notwithstanding.

With the open surface area & the larger particles, one can siphon clean the top portion of gravel easily. I have no idea how one siphon cleans a fine sandbed, unless removing & replacing sections, which many seem to do now.

FWIW, I have run bare in my last few tanks and my new 90 is also. I like the control of detritus removal also. I have rubble in mine and already its trapping detritus.

I have to admit was extremely close to setting up a plenum as I described. I really wanted to see the long term possibilities when done as above. But I cant make myself lose all that space. Not to mention the cost of a decent gravel. If I could find some of the old crushed coral, around the 5mm size, that we used on our undergravel systems, cheap, I may try still.

[albert_dao]

Originally Posted by Doug

With the open surface area & the larger particles, one can siphon clean the top portion of gravel easily. I have no idea how one siphon cleans a fine sandbed, unless removing & replacing sections, which many seem to do now.

Except any portions where you have live rock...

[Doug]

Thats why I mentioned above to limit the rock and any thats used should be elevated. We once talked about doing an sps tank with only a couple of pieces of rock, elevated above the plenum on piles {pipe}, and having most of the sps pieces attached to the glass and overflow. Nothing wrong with then having some extra rock in the sump, as long as it can be kept clean.

The limited use of rock in the tank, will also help relieve caclium demand with the coralline. The 4-5in. of gravel will provide more than enough biological filtration.

Of course this limits types of fish, that require lots of hiding places & rock, like many of the smaller fish & dwarf angels, etc. Once the sps grows, more hidey spots are there. I know if I was a fish, this would not be my favorite habitat, at least not at the start.